SSINS No. 820
OMB No.: 3150-0096
Expiration Date: 12/31/84
IEB 83-02
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 4, 1983
IE BULLETIN NO. 83-02: STRESS CORROSION CRACKING IN LARGE-DIAMETER
STAINLESS STEEL RECIRCULATION SYSTEM PIPING AT BWR
PLANTS
Addressees:
Those licensees of operating boiling water reactors (BWRs) identified in
Table 1 for action. All other licensees and holders of construction permits
(CPs) for information only.
Purpose:
IE Bulletin 83-02 is issued to further inform all licensees and CP holders
about the recent generic pipe cracking problems involving BWR plants and to
require actions of those licensees listed in Table 1.
Description of Circumstances:
As a result of the extensive intergranular stress corrosion cracking (IGSCC)
found at Nine Mile Point Unit 1, the NRC issued IE Bulletin 82-03, Revision
1 for action to nine BWR plants scheduled for refueling outages in late 1982
and early 1983. Inspections pursuant to IEB 82-03, Revision 1, and
NUREG-0313, Revision 1, have shown cracking of the main recirculation system
piping in five of seven plants examined to date. Table 2 presents a summary
of affected plants based on information available to date. IEB 82-03 Rev.1
discusses the IGSCC problems experienced at Nine Mile Point Unit 1. A brief
description of the cracking problems at Browns Ferry Unit 2, Monticello and
Hatch Unit 1 is presented below.
At Browns Ferry Unit 2, the inservice inspection (ISI) was extended to
include the welds joining the jet pump piping sweepolets to the manifold of
both A and B loops. Unacceptable indications were found in the heat-affected
zone of the manifold in the loops A and B sweepolet-to-manifold joint
nearest the end caps. All of the indications were interpreted to be cracks
near the inside surface and were determined by UT to be about 1 1/4 inches
long (roughly parallel to the weld), and of about 20 percent depth
through-wall. As a result of further design analysis, review of shop
fabrication records, and supporting in-situ metallography and ferrite
determinations, the licensee established that the affected weld was solution
heat treated and, therefore, not subject to the IGSCC. The licensee believes
the cracking may be due to fatigue from flow-induced vibration. At this time
the licensee is trying to resolve the problem.
8212060368
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IEB 83-02
March 4, 1983
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At Monticello, IGSCC was confirmed in one end-cap-to-pipe weld of the
22-inch-diameter distribution header (manifold) and at five welds in the jet
pump inlet piping safe-ends which are 12 inches in diameter and are made of
schedule 80 stainless steel. The cracks initiated on the inside surface in
heat affected zones (HAZs) of the welds. Some cracks were oriented axially
and some circumferentially. They varied from 1/4 inch to 1 inch in length.
Some axial cracks in the recirculation inlet risers were found to be
through-wall during subsequent repair activities and hydrotesting, although
ultrasonic examination previously performed on these welds did not reflect
this condition.
At Hatch Unit 1, multiple linear indications characteristic of the IGSCC
found at Monticello were identified at seven welds in the large-diameter
recirculation and associated residual heat removal (RHR) piping. The
affected welds were located as follows: All four 22-inch-diameter manifold
end-caps, one 22-inch-diameter branch connection (sweepolet-to-manifold) of
the recirculation piping, one elbow-to-pipe weld in the 20-inch RHR piping,
and one pipe-to-pipe weld in the 24-inch diameter RHR piping. The location
and orientation of the indications were very similar to those found at
Monticello. The length of the indications ranged up to 1/2 inch in the axial
direction and 1 1/2-inch in the circumferential direction. Based on UT
measurements, the depth of axial component of the crack indications were
found to have essentially penetrated through the wall in three of the four
end-cap welds repaired to date.
The discovery of extensive IGSCC in the large-diameter recirculation piping
at Nine Mile Point Unit 1 (NMP 1) after a decade of acceptable service has
resulted in increased concern about the effectiveness of UT methodology used
in the inservice inspection of stainless steel BWR pipe welds, particularly
in large-diameter piping. Therefore, the goal of Item 1 of IEB 82-03,
Revision 1 was to obtain reassurance of the capability of UT inspection
systems, techniques, and operators to detect significant IGSCC problems in
the nine BWR plants that were performing ISI during fall/winter outages. The
performance test protocol as stated in Item 1 of IEB 82-03, Revision 1
required the licensee and/or ISI agencies to demonstrate their capability to
detect IGSCC in large-diameter recirculation system piping before resuming
power operation. Within this context, Electric Power Research Institute's
NDE (EPRI-NDE) Center arranged to have five reasonably characterized,
service-induced cracked pipe samples from the NMP 1 plant available at
Battelle Columbus Laboratories (BCL) for industry performance capability
demonstrations (PCDs).
All nine plants have now satisfied the demonstration phase of IEB 82-03,
Revision 1. By letter dated January 28, 1983, EPRI provided each licensee a
summary of all teams performances, based on composite results from the five
samples, plus a key to identify their ISI team's achievement.
The PCD results at BCL have shown that excellent performance can be achieved
by well trained and experienced personnel with appropriate procedures and
evaluation methods. However, personnel from a relatively few licensee/ISI
organizations achieved this level of competence during the first
qualification attempt. The overall results revealed a high failure rate
which required retesting of the licensee/ISI organization teams. Several
interrelated factors contributed to this rate of failure:
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IEB 83-02
March 4, 1983
Page 3 of 6
1. UT procedures essentially meeting only the minimum requirements of the
ASME Section XI code were ineffective.
2. UT procedures lacked specific detailed guidance on UT systems and
methods proven capable of detecting IGSCC in thick-walled piping.
3. Some UT operators were inexperienced in evaluating signal patterns of
reflectors in thick-walled, large-diameter piping. Thus, some cracks
were missed, or were called geometry effects; some geometry effects
were falsely called cracks.
4. Many UT operators, inexperienced about the nature of IGSCC in
large-diameter piping, did not establish finite metal path calculations
during scanning; this resulted in falsely identified conditions.
In view of the collective results at BCL, a continuation of the PCD program
appears necessary. Accordingly, the EPRI-NDE Center has arranged to have a
series of service-induced cracked specimens available for this purpose at
their facility about March 14, 1983.
The NRC recognizes that the prescribed actions of this bulletin exceed
present plant ISI surveillance requirements under ASME Code Section XI
rules. However, in view of the apparently generic pipe cracking experience
and results of the UT demonstration trials, the NRC believes such an
augmented ISI plan is necessary to reasonably assure the integrity of the
recirculation system for continued operations. These actions are intended to
apply only to the currently scheduled refueling outage for those plants
listed in Table 1. Any licensee who finds these actions will significantly
impact the duration of the refueling outage may request relief by written
request to the appropriate NRC regional office. Such requests must address
(1) the impact on the length of the outage, (2) proposed alternative
actions, and (3) technical basis for continuing operation.
Actions to Be Taken by Licensees of BWR Facilities Identified in Table 1:
1. Before resuming power operations following this scheduled or extended
outage, the licensee is requested to demonstrate the effectiveness of
the detection capability of the UT methodology planned to be used to
examine welds in recircirculation system piping. It is intended that
the demonstrations be performed at the EPRI-NDE Center on
service-induced cracked pipe samples made available for this purpose.
Each licensee should assure that the demonstration is valid for the
weldments of the recirculation system piping of their plant.
Arrangements should be made to facilitate NRC witnessing of these
tests. The demonstration tests will employ the following criteria.
a. Ultrasonic Testing System: To ensure that the field UT system will
respond in the same way as the demonstrated system, the same
procedures, standards, make and model of the UT instrument, and
transducers to be utilized in the plant ISI are to be used in the
IGSCC detection capability demonstration.
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May 4, 1983
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b. Personnel Performing Demonstration: UT personnel teams drawn from the
licensees ISI contractor who will be actually supervising, performing
examinations, recording data, and evaluating indications at the plant
site will participate in the performance demonstration tests. All
members of the teams must participate directly in the UT scanning, data
recording, and evaluation of the test samples. To ensure completion of
testing within the time constraints below, the team should be limited
to six persons. For subsequent plant inspections, the
personnel/equipment requirements noted below will apply.
c. Pipe Samples: The total number of pipe samples selected should
constitute an equivalent of 120 inches of weld for the demonstration
tests.
d. Acceptable Criteria: Eighty percent of the total number of preselected
cracks in the sample control group must be called correctly to
constitute an acceptable test. Excessive false call rates may result in
an unacceptable performance rating.
e. Demonstration Time Limit: ALARA radiation dose considerations place
constraints upon the time spent in field inservice inspection of a
weld. Therefore, a time limit of six hours, not including equipment
calibration time, will be imposed for the examination and data
recording. Completion of data evaluation and preparation of final
results of individual licensee/ISI contractors should take no longer
than one additional working day.
f. Review of UT Procedures: The specific procedure(s) to be used by the
licensee/ISI contractor(s) for plant inservice inspection is to be made
available for review as part of the demonstration activity. It is
expected that the UT procedure and equipment system will have been
validated to be capable of detecting IGSCC by the licensee/ISI
contractor before initiating the scheduled demonstration activities.
NOTE: Some of the licensees listed in Table 1 have completed efforts to
validate the UT detection capability to be used to perform plant
inspections in accordance with the requirements of Action Item I of IEB
82-03, Revision 1. These licensees need not repeat this effort in
accordance with Action Item 1 of this bulletin provided that the
previous validated inspection group performs the new plant examination
using identical UT procedures, standards, make and model of UT
instrument, and the same make and model transducers that were used to
complete the previous validation effort. In addition, the UT personnel
employed in the new examination must be the same; or those having
appropriate training (documented) in IGSCC inspection using cracked
thick-wall pipe specimens, and are under direct supervision of the
Level II/III UT operators who successfully complete the performance
demonstration tests.
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March 4, 1983
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2. Before resuming power operations licensees are to augment their ISI
programs to include an ultrasonic examination of the following minimum
number of recirculation system welds:
a. Ten welds in recirculation piping or 20-inch diameter, or larger.
b. Ten welds of the jet pumps inlet riser piping and associated
safe-ends.
c. Two sweepolet-to-header (manifold) welds of jet pump risers
nearest the end caps, if applicable to the design.
If flaws indicative of cracking are found in the above examination,
additional inspection is to be conducted in accordance with IWB 2430 of
ASME Code Section XI.
3. Before resuming power operations following the outage, the licensee is
to report the results of the Item 2 inspection and any corrective
actions (in the event cracking is identified). This report should also
include the susceptibility matrix used as a basis for welds selected
for examination (e.g. stress rule index, carbon content, high stress
location, repair history) and their values for each weld examined.
4. The NRC has an on-going program to evaluate possible additional
longerterm requirements relative to the IGSCC problem in the BWR
recirculation system piping. The NRC may need additional information as
part of this program. Therefore, licensees are requested to retain the
records and data developed pursuant to the inspections performed in
accordance with Item 2.
5. The written report required by Item 3 shall be submitted to the
appropriate Regional Administrator under oath or affirmation under
provisions of Section 182a, Atomic Energy Act of 1954, as amended. The
original copy of the cover letter and a copy of the reports shall be
transmitted to the U.S. Nuclear Regulatory Commission, Document Control
Desk, Washington, D.C. 20555 for reproduction and distribution.
This request for information was approved by the Office of Management and
Budget under clearance number 3150-0096 which expires 12/31/84. Comments on
burden and duplication should be directed to the Office of Management and
Budget, Reports Management, Room 3208, New Executive Office Building,
Washington, D. C. 20503.
Since Big Rock Point and LaCrosse do not have jet pumps, the licensees
of these plants should provide an equivalent sampling of the
recirculation piping system based on the plant design.
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IEB 83-02
March 4, 1983
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Although no specific request or requirement is intended, the following
information would help the NRC evaluate the cost of implementing this
bulletin:
o Staff time to perform requested demonstration.
o Staff time to prepare written responses.
o The occupational radiation exposure experienced.
If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC Regional Office or one of the technical
contacts listed below.
Richard C. DeYoung, Director
Office of Inspection and Enforcement
Technical Contact: William J. Collins, IE
492-7275
Warren Hazelton, NRR
492-8075
Attachments:
1. Table 1
2. Table 2
3. List of Recently Issued IE Bulletins